Underwater tool

ABSTRACT

To obviate the need for hydraulic lines, from the surface, external water pressure is used to compress a seal member and form a seal with a surrounding pip. Valve is opened at depth to allow water to act on a piston, moving it within a chamber so as to compress the seal member. A second valve may be opened so that water acts on the opposite end of the piston to release the seal member.

[0001] This invention concerns a tool for use in deep water, which toolconsists of or includes a sealing device.

[0002] Such a tool, with a sealing device, may be used for recovery ofpipelines from such great depths that all work has to be carried out byremotely operated vehicles, as opposed to divers. A number of knowntools of this type use hydraulic pressure to operate the sealing device,whereby the tool fastens itself to a pipe section, for hauling same backto the surface. Obviously, these tools rely on having a hydraulic lintfrom the surface to the tool, which may be on the sea bed.

[0003] An object of the present invention is to obviate the need forsuch a hydraulic line.

[0004] According to the present invention, in a sealing device of anunderwater tool, external water pressure at depth can act on a piston,which is movable within a chamber, to cause it to compress a sealmember.

[0005] The invention will be described further, by way of example, withreference to the accompanying drawings, in which:

[0006]FIG. 1 is a schematic sectional view of a pipe and of a sealingdevice according to the invention, which will locate in the pipe; and

[0007]FIG. 2 is a perspective view of a pipeline recovery tool fittedwith a sealing device similar to that shown in FIG. 1.

[0008] Referring to FIG. 1, the exemplary sealing device comprises acylindrical housing (10) having a central through bore (12). An annularchamber (14) is formed in the housing (10) and an annular piston (16) isaxially slidable within this chamber (14). The piston (16) islongitudinally shorter than the chamber (14) so that a space remainswithin the chamber at one or both ends of the piston (16), depending onits position ,therein. Two O-ring seals (18) are provided between thepiston (16) and the radially inner wall of the chamber (14), andsimilarly two O-ring seals (19) are provided between the piston (16) andthe radially outer wall of the chamber (14). A lateral extension (26) ofthe piston (16) projects into an opening in the housing (10) adjacent anannular sealing member (20) which may be of any conventional deformablepacking material, such as rubber or synthetic rubber or substitutestherefor. Movement of the piston (16) in the direction indicated byarrow “A” causes its lateral extension (26) to compress and deform thesealing member (20) causing it to bulge outwardly. Thus, when thehousing (10) is a close fit inside a pipe section (30), a tight seal canbe created between the housing (10) and the pipe interior by movement ofthe piston (16) in the direction of arrow “A”.

[0009] A first inlet in the form of a conduit (22) leads into one end ofthe chamber (14) from the exterior and is fitted with a first shut offvalve (24). A second inlet in the form of a conduit (28) leads into theopposing end of the chamber (14) from the exterior and is fitted with asecond shut off valve (29) .

[0010] At the surface, before submersion of the sealing device, thechamber (14) is filled with air at normal atmospheric pressure and thevalves (24) and (29) are closed. The sealing device is then lowered tothe sea bed and, by means of a remotely operated vehicle (not shown), ismanoeuvred into position inside the pipe section (30) awaiting recovery.The vehicle then opens the first valve (24) for about a minute to allowwater through the conduit (22) into the first end of the chamber (14),thus moving the piston (16) in direction “A” and compressing the seal(20) to engage the pipe (30). The valve (24) is then closed to maintainthe pressure on the seal (20) as the pipe (30) is recovered to thesurface.

[0011] If it is necessary to disengage the sealing device housing (10),from the pipe (30) while the latter is still on or neat the sea bed, thevehicle can open both the valves (24) and (29) to allow water to enteraria both the conduits (22) and (28) and equalise pressure at therespective ends of piston (16) The seal (20) will then recover back toits original shape and size and disengage the pipe (30).

[0012] The sealing device housing (10) would then have to be returned tothe surface for resetting of the piston (16), i.e. replenishing thechamber (14) with air and closing off the valves (24) and (29) again.

[0013]FIG. 2 simply shows at (40) where a device such as that in FIG. 1can be incorporated in a larger Ballgrab recovery tool. Such a tooladvantageously includes means for pumping water out of the pipe (30) viathe throughbore (12), to aid its recovery. A check valve (32) in thebore (12) can be used to prevent backflow of water as it is pumped out.

[0014] The foregoing is illustrative and not limitative of the scope ofthe invention and many variations in detail are possible.

1. A tool for use under water comprising a sealing device whereinexternal water pressure at depth can act on a piston (16) which ismovable within a chamber (14), to cause it to compress a seal member(20).
 2. A tool according to claim 1 having a valve actuated inlet (22,24) to the chamber (14) at a first end of the piston (16) wherebyexternal water pressure may act on the piston to compress the sealmember (20).
 3. A tool according to claim 2 having a second valveactuated inlet (28, 29) to the chamber (14) at an opposing end of thepiston (16) whereby external water pressure may act on the piston torelease the seal member (20).
 4. A tool according to claim 1, 2 or 3wherein the seal member (20) is annular.